1. Field of the Invention
The present invention is generally related to a lubrication system for an internal combustion engine and, more particularly, to a lubrication system that conducts residual oil from a crankcase of a two cycle engine to a cylinder bore of the engine.
2. Description of the Prior Art
Internal combustion engines require lubrication to prevent damage to engine components which move in a sliding relationship with other engine components. Certain types of internal combustion engines, such as some two cycle engines, provide oil in a mixture of fuel so that the oil is carried through the crankcase of the engine to lubricate the crankcase, connecting rods, and piston of each cylinder. Some engines inject oil directly into the crankcase at a position where incoming air flow will carry the oil throughout the crankcase and lubricate the moving components of the engine.
When an internal combustion engine is operating at a sufficiently high speed, the flow of air through the crankcase will generally be sufficient to distribute the oil, as a mist, to all portions of the crankcase. However, under certain conditions, residual oil can collect in puddles within the crankcase. If sufficient air flow is not available to distribute the oil, as a mist, throughout all regions of the crankcase, two significant problems can occur. First, certain portions of the pistons and connecting rods can be deprived of sufficient lubrication to prevent damaging wear and excessive heat caused by friction. In addition, the residual oil that collects in puddles within the crankcase will eventually be drawn from the crankcase and into the combustion chambers of the engine. This excessive oil can severely affect the operating quality of the engine and foul the spark plugs. It is generally known to those skilled in the art that residual oil can be conducted from the puddles in the crankcase to the combustion chamber where it is burned so that excessive accumulation of residual oil in the crankcase does not occur.
Another problem that can occur in internal combustion engines is the insufficiency of lubrication on the cylinder walls to prevent excessive wear and heat buildup from friction as the piston moves reciprocally within the cylinder. Under proper conditions, oil which is introduced at the air intake of a crankcase will be carried by the air, as a mist, into contact with the cylinder wall below the piston and the other moving components such as the connecting rods and crankshaft. However, if the airflow through the crankcase is insufficient to carry the oil mist into contact with these portions of the engine, the cylinder wall may not receive sufficient lubrication to prevent wear and excessive heat buildup resulting from the friction between the moving pistons and the stationary cylinder walls. This condition, where insufficient oil is carried by the air into contact with the moving components of the engine, is most likely to occur when the engine is operating at relatively low speeds such as when the engine is idling. Many different methods have been used by those skilled in the art to address the issues of residual oil removal from the crankcase and lubrication of the cylinder walls of an internal combustion engine.
U.S. Pat. No. 4,945,846, which issued to Solomon et al on Aug. 7, 1990, describes a two cycle engine piston lubrication. A two cycle engine has oil distribution means through the cylinder wall to feed internal oil passages in the associated piston that distribute oil directly to the skirt and cylinder walls. The oil is preferably fed between ports and/or to the wrist pin and connecting rod bearing to thereby limit oil carryover into the engine charging and scavenging air.
U.S. Pat. No. 5,115,791, which issued to Dore on May 26, 1992, discloses an engine crankcase with crankcase gas exhaust and oil recirculation systems. The device relates to a crankcase or cylinder block for an internal combustion engine of any type, for example, of the V or in-line cylinder type. The upper half of the crankcase comprises internal conduits which connect the upper part of the crankcase with the lower compartments separating the crankcase bearings, these conduits making possible the exhaust of crankcase gases and the recycling of the engine oil and opening into a chamber of a flat shape, with the chamber and the internal conduits forming an integral as-cast system. The system is particularly applicable to the automotive industry.
U.S. Pat. No. 4,672,931, which issued to Biagini on Jun. 16, 1987, describes a lubrication system with oil recovery for a two-stroke engine piston with pump-sump for scavenging. The lubrication system has an oil recovery capability for a two-stroke engine piston with pump-sump for scavenging. The system consists of a lubricating oil pressure circulation system having inlet and outlet holes for the oil. The holes pass through the wall of the cylinder. The system also comprises shaped scraper rings, wherein each ring is housed within a circular housing or seat obtained on the outside skirt of the piston. The circular housings are provided on the skirt of the pistons at a height which does not allow any overlapping of the scraper rings on the transfer ports of the two-stroke engine.
U.S. Pat. No. 4,926,814, which issued to Bonde on May 22, 1990, discloses a crankcase breather and lubrication oil system for an internal combustion engine. The engine has a vertically oriented crankshaft and a horizontally oriented cylinder bore and includes a plurality of lubrication sites to be pressure lubricated. A first upstanding wall extends upwardly from the top wall of the crankcase and circumscribes and defines a first chamber. A breather passage communicates crankcase gases from the crankcase into the first chamber. A drain passage communicates oil separated from the crankcase gases in the first chamber into the cylinder bore below the piston and its positioned along the cylinder bore so as to be periodically occluded by the piston during reciprocation thereof. A second upstanding wall extends upwardly from the top wall of the crankcase in spaced relationship to at least a portion of the first wall, and defined together with the first wall a second chamber therebetween. A first oil passage communicates oil from the a lubricant pump to the second chamber, and a second oil passage communicates from the second chamber to at least one of the lubrication sites.
U.S. Pat. No. 4,993,380, which issued to Hsu on Feb. 19, 1991, discloses a lubrication mechanism of an engine cylinder. The mechanism includes upper and lower ring troughs on the inside wall of the engine cylinder. The two ring troughs can accommodate oil pipes and ring oil nets. The oil pipes include an inlet pipe and an outlet pipe. Channels and numerous oil pores are defined by the pipes to allow the entrance of lubricating oil into the oil pipes and seepage from the pores on the oil pipe through a ring oil net to provide lubrication to the inside wall of the cylinder. The lubricating oil then flows downwardly to the lower ring oil net, through the net and the oil pipe, and into an outlet pipe for discharge.
The patents described immediately above are hereby explicitly incorporated by reference in the following description.
In view of the above discussion, it can be seen that it would be significantly beneficial if a simple and cost effective means could be provided to collect residual oil in the crankcase of an internal combustion engine and conduct that oil directly to the bores of cylinders within the engine.